Capacity vs. generation

Capacity is the maximum output a piece of generating equipment can produce, expressed in megawatts (MW); this is a rated, potential figure. Generation is the actual amount of electric energy produced over a period of time, expressed in kilowatt-hours or megawatt-hours; this is a real, historical figure. A power plant's capacity doesn't change from day to day, but its generation does, depending on demand, fuel availability, weather (for solar and wind), and maintenance. Confusing the two is one of the most common errors in casual energy reporting.